Abstract Extracellular vesicles (EVs) are cargo carrying, quasi-nanovesicles that mediate intercellular communication. EVs are released by many cell types and are present in body fluids. The composition and function of EVs mirror that of the producing environment. Thus, EVs are implicated in regulating microbial pathogenesis, extracellular matrix reorganization, epithelial barrier dysfunction, and inflammatory cell recruitment. Indeed, we and others have shown that exosomes from body fluids, such as vaginal fluid and semen possess anti-HIV activity, and that use of drugs of abuse reprograms exosome phenotype and function. The goal of this multi-PI proposal is to leverage our expertise and resources to evaluate how cannabinoid (delta-9-tetrahydrocannabinol, THC) modulates the composition and function of EVs during HIV/SIV infection, focusing on the gastrointestinal tract (GI) and peripheral lymph nodes using the SIV-rhesus macaque model. HIV-infected (HIV+) patients are often comorbid with drug abuse and cannabis (marijuana) is one of the most commonly used drugs of abuse in the setting of HIV comorbidity. Approximately, 15?40% of HIV/AIDS patients use cannabis to treat disease symptoms and ameliorate side effects due to combinatorial antiretroviral therapy (cART). Recent research findings indicate that administration of THC?the most psychoactive anti-inflammatory cannabinoid in cannabis is linked to beneficial reduction in systemic inflammation and immune activation in cART-treated HIV+ patients. In the SIV/macaque model, THC ameliorated SIV disease progression, reduced intestinal T cell activation/exhaustion and prevented lymph node fibrosis. The benefits of THC is systemic?affecting many organs, including the GI and lymphoid systems. Gap in knowledge - The underlying mechanisms of THC- mediated reduction in systemic inflammation, immune activation, and lymph node fibrosis in HIV/SIV infection is unclear. Since 30 U.S. states allow the use of cannabinoids for medical purposes, with citations of HIV/AIDS as a condition amenable to such treatment; it is important to understand how THC regulates inflammation and disease progression in this population. Our preliminary data show that SIV infection results in a time-dependent increase in the release of proinflammatory EVs (VEH/SIV EV) that promote expression of inflammatory markers and cytoskeletal remodeling in monocytes and T cells. In contrast, chronic treatment with THC results in secretion of THC/SIV-EV that are lower in number, carry anti-inflammatory molecules, and counteracts VEH/SIV EV- induced cytoskeletal remodeling. Based on our published studies and these pilot data, our overarching hypotheses are that SIV infection of rhesus macaques (RMs) results in the shedding of VEH/SIV EV containing pro-inflammatory and pro-fibrogenic factors that promote chronic inflammation, epithelial barrier dysfunction, microbial translocation, and lymphoid fibrosis. Furthermore, chronic THC treatment in the setting of cART may reduce inflammation, microbial dysbiosis, lymphoid fibrosis, and restore immune function by modulating EV secretion and their cargo.